The present invention relates to a technique of controlling the quantity of light when a person approaches the path of projection rays emitted from a projector.
A projector widely used for presentation is an image display apparatus that projects light (projection rays) representing an image in response to an image signal output from an image supply apparatus, such as a computer, so as to display the image. The user performs the presentation while pointing out the image projected on the screen.
When the image is projected onto the screen from the projector located in front of the screen (such projection is referred to as xe2x80x98front projectionxe2x80x99), there is a space between the projector and the screen to allow the pass of the projection rays. The user or another person may thus approach the path of the projection rays. In such cases, when the person shifts the line of sight toward the projector, the projection rays directly enter the filed of vision of the person. The person may directly look at the projection lens to check if the projector normally works. In this case, the person may be dazzled and feel unpleasant. The designed luminous flux of the projection rays output from the projector tends to gradually increase, which may worsen the user""s feeling of unpleasantness.
The object of the present invention is thus to solve the above drawbacks of the prior art technique and to provide a technique of controlling the output luminous flux of projection rays output from a projector, so as to relieve the unpleasantness due to the direct incidence of the projection rays into the field of vision of a person.
At least part of the above and the other related objects of the present invention is attained by a projector including an electro-optic device that outputs rays modulated according to a given image signal, an image processing unit that transmits the image signal to the electro-optic device, and a luminous flux control device that controls an output luminous flux of projection rays, which are output from the electro-optic device and projected. The luminous flux control device has: a detector unit that detects a person who approaches a path of the projection rays; and a controller unit that controls the output luminous flux of the projection rays when the detector detects the approach of the person.
When a person approaches the path of the projection rays and the projection rays directly enter the filed of vision of the person, the projector of the present invention detects the approach of the person and controls the output luminous flux of the projection rays. This arrangement effectively relieves the unpleasantness due to the direct incidence of the projection rays output from the projector into the field of vision of the person.
In a first preferable application of the projector of the present invention, the detector unit includes: a luminance detector having a light receiving unit that is disposed in a neighborhood of a projection lens, from which the projection rays are output, and receives reflected rays obtained by reflection of the projection rays, the luminance detector outputting a reflection luminance of the reflected rays received by the light receiving unit as a reflection luminance signal; a reference luminance level generator that specifies a reference luminance based on a luminance signal level of an image signal corresponding to the projection rays, and outputs the specified reference luminance as a reference luminance signal; and a luminance comparator that compares the reflection luminance signal with the reference luminance signal. The controller unit controls the output luminous flux of the projection rays according to an output of the luminance comparator.
This arrangement facilitates the construction of the detector unit and the controller unit of the luminous flux control device.
The reflection luminance of the reflected rays detected by the luminance detector varies with a variation in output luminous flux of the projection rays. It is accordingly desirable that the reference luminance signal output from the reference luminance level generator varies with the variation in output luminous flux of the projection rays. The reference luminance level generator in the first application specifies the reference luminance based on the luminance signal level of the image signal corresponding to the projection rays. This arrangement thus enables the output reference luminance signal to be varied with a variation in output luminous flux of the projection rays.
In a second preferable application of the projector of the present invention, the image processing unit has a reference image signal generator that generates a reference image signal, which is used to output the projection rays corresponding to a preset luminance signal level, and transmits the reference image signal to the electro-optic device. The detector unit includes: a luminance detector having a light receiving unit that is disposed in a neighborhood of a projection lens, from which the projection rays are output, and receives reflected rays obtained by reflection of the projection rays, the luminance detector outputting a reflection luminance of the reflected rays received by the light receiving unit as a reflection luminance signal; a reference luminance level generator that registers, as a reference luminance signal, a reflection luminance output from the luminance detector when the projection rays corresponding to the preset luminance signal level are output in response to the reference image signal; and a luminance comparator that compares the reflection luminance signal with the reference luminance signal. The controller unit controls the output luminous flux of the projection rays according to an output of the luminance comparator.
Like the first application, the second application facilitates the construction of the detector unit and the controller unit. While the reference luminance level generator in the first application varies the reference luminance signal with a variation in output luminous flux of the projection rays, the reference luminance level generator in the second application sets the reflection luminance in response to the preset luminance signal level to the reference luminance signal. The second application, however, exerts the similar functions and effects to those of the first application.
In a third preferable application of the projector of the present invention, the detector unit includes: a luminance detector having an infrared emission unit and an infrared receiving unit that are disposed in a neighborhood of a projection lens, from which the projection rays are output, the infrared receiving unit of the luminance detector receiving reflected rays of infrared radiation emitted from the infrared emission unit, the luminance detector outputting a reflection luminance of the received reflected infrared rays as a reflection luminance signal; and a luminance comparator that compares the reflection luminance signal with a preset reference luminance signal. The controller unit controls the output luminous flux of the projection rays according to an output of the luminance comparator.
In a fourth preferable application of the projector of the present invention, the detector unit includes: an ultrasonic wave detector having an ultrasonic wave transmitter unit and an ultrasonic wave receiver unit that are disposed in a neighborhood of a projection lens, from which the projection rays are output, the ultrasonic wave receiver unit of the ultrasonic wave detector receiving a reflected wave of an ultrasonic wave transmitted from the ultrasonic wave transmitter unit, the ultrasonic wave detector measuring a strength of the received ultrasonic wave; and an ultrasonic wave comparator that compares the measurement of the received ultrasonic wave strength with a preset reference received ultrasonic wave strength. The controller unit controls the output luminous flux of the projection rays according to an output of the ultrasonic wave comparator.
In a fifth preferable application of the projector of the present invention, the detector unit includes: an ultrasonic wave transmitter unit that is disposed in a neighborhood of a projection lens, from which the projection rays are output; an ultrasonic wave receiver unit that is disposed in the neighborhood of the projection lens and receives a reflected wave of an ultrasonic wave transmitted from the ultrasonic wave transmitter unit; a time measurement unit that continues measuring time between transmission of the ultrasonic wave from the ultrasonic wave transmitter unit and receipt of the ultrasonic wave by the ultrasonic wave receiver unit; and a time comparator that compares the observed time by the time measurement unit with a preset reference time. The controller unit controls the output luminous flux of the projection rays according to an output of the time comparator.
Like the first and the second applications, these third to fifth applications simplify the construction of the detector unit and the controller unit.
In accordance with one preferable embodiment of the projector, the luminous flux control device further has an information unit that, when the controller unit controls the output luminous flux of the projection rays, informs the person of the controlled output luminous flux of the projection rays.
This arrangement readily informs the person of the fact that the person approaches the path of the projection rays and thereby the output luminous flux of the projection rays is controlled.